In recent years, the development of preventives and remedies for various viral infections has attracted particular attention with the advance of researches into pathogenic viruses.
Antiviral agents for use in chemotherapy heretofore proposed for clinical purposes are idoxuridine, cytarabine, vidarabine, acyclovir and the like. (See, for example, Yutaka Mizushima and Terumasa Miyamoto, The Edition of 1986, "Konnichi no Chiryo-yaku (Present-Day Remedies), Kaisetsu to Binran (Explanation and Manual)", Nanko-do, pp. 47-50 (Mar. 10, 1986).)
Most of the above-mentioned drugs, however, have been accompanied by problems including limited clinical applicability due, for instance, to antiviral activity spectra, low absorption, poor solubility, easy decomposition, the advent of drug-fast virus strains, and various side effects. Accordingly, there has been an urgent demand for the development of novel antiviral agents.
A primary object of the present invention is to provide novel compounds having remarkable antiviral activities.